servlet实现动态验证码

package com.dream.servlet;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

/**
 * @author ZhangJun
 * @date 2020-04-08
 * @description 服务器向客户端输出字节数据
 */
@WebServlet("/checkCodeServlet")
public class CheckCodeServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        int width=100;
        int height=50;
        //1.创建一个对象，在内存中代表一个图片【验证码的图片对象】
        BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);


        //2.美化图片
        //2.1填充背景色 fillRect【填充】
        Graphics graphics = image.getGraphics();
        graphics.setColor(Color.PINK);//设置画笔颜色
        graphics.fillRect(0,0,width, height);

        //2.2画边框 drawRect【画线条】
        graphics.setColor(Color.BLUE);
        graphics.drawRect(0, 0, width-1, height-1);

        String str ="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
        //生成随机角标
        Random random = new Random();
        for (int i = 1; i <=4; i++) {
            int index = random.nextInt(str.length());
            //获取字符
            char cha = str.charAt(index);
            //2.3写验证码
            graphics.drawString(cha+"", width/5*i, height/2);
        }
        //2.4画干扰线
        graphics.setColor(Color.green);
        for (int i = 0; i < 10; i++) {
            //随机生成坐标点
            int x1 = random.nextInt(width);
            int x2 = random.nextInt(width);
            int y1 = random.nextInt(height);
            int y2=  random.nextInt(height);
            graphics. drawLine(x1, y1, x2, y2);
        }

        //3.将图片输出到界面展示：使用ImageIO对象
        //resp.getOutputStream() : 输出到页面，浏览器上
        ImageIO.write(image, "jpg", resp.getOutputStream());
    }
}